Excel 2016 Pro Plus - false error of "file damaged" on mail or network after windows update.

Hi,

after a Microsoft update on 11th Nov (don't know if a coincidence or not) Excel gives a "file damaged" error (only this text, no other error code) when opening a file from an email in Outlook or from a network path.

The issue happened to 3 PCs, all the same day and all after updates.

Here is some details:

• updates included malware definition (KB890830), build cumulative update (KB5031356) and framework cumulative update (KB5031224).
• copy paste the file (from an email or network path) on the desktop solve the problem quite always, weirdly not always.
• disabling protected view in excel Trust Center definitely "solve" the problem. but seems not a good idea to me.
• I already tried in vain to repair office, unistall office e reinstall it at an older version, and sfc /scannow on Windows, uninstall the build update (can't uninstall the malware definition update of course).

Thank you in advance ofr your help.